refactor: break monorepo into 3 standalone services (gateway, backend, frontend)

- Remove pnpm workspace, moon repo, and all monorepo tooling
- Delete packages/shared/, embed shared code directly into each service
- Copy packages/shared/src/* -> services/backend/src/shared/ and services/discord-gateway/src/shared/
- Replace all @bete/shared imports with @/shared/ path alias
- Remove @bete/shared workspace dependency from both services
- Update root package.json scripts from --filter to --prefix
- Rewrite Dockerfiles to build each service standalone
- Clean up biome.json, .gitignore, remove root drizzle.config.ts

services/discord-gateway/src/modules/command-handler/commandHandler.ts

@@ -4,8 +4,8 @@ import {
   type CommandReply,
   MEDIA_STATUS_KEY,
   VOICE_STATUS_KEY,
-} from "@bete/shared";
-import { createChildLogger } from "@bete/shared/logger";
+} from "../../shared/index.js";
+import { createChildLogger } from "../../shared/logger/index.js";
 import type { Client } from "discord.js-selfbot-v13";
 import Redis from "ioredis";
 import { config } from "../../shared/config/config.js";